The invention relates to a coating machine, and more particularly, a coating machine for coating fabric traveling on the rails of a tenter frame in which an automatic feed trough system closes at tenter stop and opens to a preset position at tenter start.
It is known to support a coating compound above a fabric traveling through a coating machine by means of a trough. A gap between a free edge of the trough and a coating blade allows the coating compound to be deposited on the fabric traveling through the machine and scraped into or applied onto the fabric by the coating blade. One parameter that controls the characteristic of the coating on the fabric is the sink rate. The sink rate is the sink or absorption rate of the coating compound into the fabric which is determined by the amount of time that the coating compound is allowed to stand on the fabric. Utilizing a trough, the coating compound is supported above the surface of the fabric and thus the sink rate may be controlled. A gap may be set between the edge of the trough and the coating blade. This determines the amount of coating compound that is allowed to stand on the fabric and the sink rate.
The problem occurs that when such an apparatus is utilized to coat the fabric traveling on a tenter rail, the tenter is susceptible to stoppage. When the tenter stops, the fabric stops, and the coating compound is allowed to stand and absorb into the fabric longer than usual which alters the coating characteristics. The coating characteristic is also controlled by the pressure between the fabric, as supported on a surface, and the coating blade.
The problem also occurs on such machines of accommodating the passage of a thickened seam portion beneath the coating blade. Typically, such a machine utilizes a support surface over which the fabric travels and against which the fabric is held against the coating blade. When the thickened seam portion approaches the coating blade, impact forces are encountered by the coating blade and the seam since the close clearance between the blade and the support surface do not provide enough space for seam passage. Seam damage and uneven coating occurs in this area. Coating on a foam table lessens impact but provides non-uniform coating in the seam area since the pressure on the foam table is relatively uncontrollable.
U.S. Pat. No. 4,056,423 discloses a rotatable chute which varies the size of an opening through which a material is dispensed. U.S. Pat. No. 4,450,226 discloses a liquid manifold and movable gate which varies an opening in the manifold. Apparently, the gate can also be used to close the manifold. While the above are suitable for their intended applications, the like would not be suitable for trough feeding systems of coating apparatus of the type herein.
U.S. Pat. No. 4,308,823 discloses a coating apparatus which compensates for knot passage. The effective size of the entrance to the coating chamber is increased in order to allow the knots to pass.
In U.S. Pat. No. 4,095,063 a device for detecting a local thickening in a web of paper or film is disclosed. A pivotal sensor roller is utilized over a stationary roller. Pivoting of the roller in response to the passage of a thickening is detected by pivoting of the roller. Similarly, a spring biased roller is disclosed in U.S. Pat. No. 2,614,522 which supports a flexible sheet being coated. The purpose of the spring mounted roller is to maintain the applicator roll in a slightly retracted position in order to prevent the application of coating to the leading edge of the sheet. While spring biased pivoted rollers and vertically displaceable rollers have been known in certain types of coating environments, they have not been devoted to problems inherent in the passage of a thickened seam portion in a coating machine, nor to the solution of the problem provided by the present invention.
Accordingly, an important object of the present invention is to provide a coating machine which is particularly useful for coating fabric traveling on a tenter.
Another important object of the present invention is to provide coating apparatus having a trough feed system wherein the trough automatically closes when the tenter stops and opens to a preset gap position when the tenter starts.
Yet another important object of the present invention is to provide a coating machine having a roll mandrel assembly which deflects in an arcuate motion to allow for seam passage.
Still another important object of the present invention is to provide a roll mandrel for supporting a fabric on a coating machine which deflects in a rearward arcuate motion to allow for seam passage and returns automatically at a constant pressure to a coating position.